U.S. patent application number 14/333885 was filed with the patent office on 2016-01-21 for systems and methods for an improved peel operation during additive fabrication.
This patent application is currently assigned to Formlabs, Inc.. The applicant listed for this patent is Formlabs, Inc.. Invention is credited to Ben FrantzDale, Maxim Lobovsky, Steven Thomas.
Application Number | 20160016361 14/333885 |
Document ID | / |
Family ID | 55073851 |
Filed Date | 2016-01-21 |
United States Patent
Application |
20160016361 |
Kind Code |
A1 |
Lobovsky; Maxim ; et
al. |
January 21, 2016 |
SYSTEMS AND METHODS FOR AN IMPROVED PEEL OPERATION DURING ADDITIVE
FABRICATION
Abstract
According to some aspects, a method of additive fabrication
wherein a plurality of layers of material are formed on a build
platform is provided. The method may comprise forming a layer of
material in contact with a container, and subsequent to the forming
of the layer of material, rotating the container relative to the
build platform and moving the build platform relative to the
container, thereby creating an effective fulcrum about an axis,
wherein the rotating of the container and moving of the build
platform causes the layer of material to separate from the
container. According to some embodiments, the container may be
configured to rotate about a fixed axis. According to some
embodiments, moving the build platform may comprise moving the
build platform toward the container.
Inventors: |
Lobovsky; Maxim; (Cambridge,
MA) ; Thomas; Steven; (Cambridge, MA) ;
FrantzDale; Ben; (Shrewsbury, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Formlabs, Inc. |
Somerville |
MA |
US |
|
|
Assignee: |
Formlabs, Inc.
Somerville
MA
|
Family ID: |
55073851 |
Appl. No.: |
14/333885 |
Filed: |
July 17, 2014 |
Current U.S.
Class: |
264/308 ;
425/165 |
Current CPC
Class: |
B33Y 10/00 20141201;
B29C 64/393 20170801; B29C 64/245 20170801; B29C 64/135 20170801;
B29C 64/255 20170801; B33Y 50/02 20141201; B33Y 30/00 20141201 |
International
Class: |
B29C 67/00 20060101
B29C067/00 |
Claims
1. A method of additive fabrication wherein a plurality of layers
of material are formed on a build platform, comprising: forming a
layer of material in contact with a container; and subsequent to
the forming of the layer of material, rotating the container
relative to the build platform and moving the build platform
relative to the container, thereby creating an effective fulcrum
about an axis, wherein the rotating of the container and moving of
the build platform causes the layer of material to separate from
the container.
2. The method of claim 1, wherein rotating the container comprises
rotating the container about an end of the container.
3. The method of claim 1, wherein the container is configured to
rotate about a fixed axis.
4. The method of claim 1, wherein moving the build platform
comprises moving the build platform toward the container.
5. The method of claim 1, further comprising identifying the axis a
first distance from an end of the container, and creating the
effective fulcrum about the axis.
6. The method of claim 1, wherein the layer of material is formed
such that it at least partially adheres to the container.
7. The method of claim 1, wherein the layer of material is formed
in contact with a previously formed layer.
8. The method of claim 1, further comprising determining a position
of the axis based at least in part on a size and/or position of the
layer of material.
9. The method of claim 8, wherein the axis is determined based at
least in part on a distance from an end of the container to an edge
of the layer of material.
10. An additive fabrication apparatus configured to form a
plurality of layers of material on a build platform, comprising: a
container; the build platform; one or more actuators; and at least
one controller configured to: rotate the container relative to the
build platform via at least one of the one or more actuators; move
the build platform relative to the container via at least one of
the one or more actuators; and subsequent to formation of a layer
of material in contact with the container, rotate the container and
move the build platform, thereby creating an effective fulcrum
about an axis, wherein the rotating of the container and moving of
the build platform causes the layer of material to separate from
the container.
11. The apparatus of claim 10, wherein the at least one controller
is configured to rotate the container about an end of the
container.
12. The apparatus of claim 10, wherein moving the build platform
comprises moving the build platform toward the container.
13. The apparatus of claim 10, wherein the at least one controller
is further configured to identify the axis a first distance from an
end of the container, and create the effective fulcrum about the
axis.
14. The apparatus of claim 10, wherein the axis is determined based
at least in part on a size and/or position of the layer of
material.
15. The apparatus of claim 14, wherein the axis is determined based
at least in part on a distance from an end of the container to an
edge of the layer of material.
16. At least one computer readable medium comprising instructions
that, when executed, perform a method of additive fabrication
wherein a plurality of layers of material are formed on a build
platform, the method comprising: forming a layer of material in
contact with a container; and subsequent to the forming of the
layer of material, rotating the container relative to the build
platform and moving the build platform relative to the container,
thereby creating an effective fulcrum about an axis, wherein the
rotating of the container and moving of the build platform causes
the layer of material to separate from the container.
17. The at least one computer readable medium of claim 16, wherein
the container is configured to rotate about a fixed axis.
18. The at least one computer readable medium of claim 16, wherein
moving the build platform comprises moving the build platform
toward the container.
19. The at least one computer readable medium of claim 16, further
comprising identifying the axis a first distance from an end of the
container, and creating the effective fulcrum about the axis.
20. The at least one computer readable medium of claim 16, further
comprising determining a position of the axis based at least in
part on a size and/or position of the layer of material.
Description
FIELD OF INVENTION
[0001] The present invention relates generally to systems and
methods for separating a part from a surface during additive
fabrication, e.g., 3-dimensional printing.
BACKGROUND
[0002] Additive fabrication, e.g., 3-dimensional (3D) printing,
provides techniques for fabricating objects, typically by causing
portions of a building material to solidify at specific locations.
Additive fabrication techniques may include stereolithography,
selective or fused deposition modeling, direct composite
manufacturing, laminated object manufacturing, selective phase area
deposition, multi-phase jet solidification, ballistic particle
manufacturing, particle deposition, laser sintering or combinations
thereof. Many additive fabrication techniques build parts by
forming successive layers, which are typically cross-sections of
the desired object. Typically each layer is formed such that it
adheres to either a previously formed layer or a substrate upon
which the object is built.
[0003] In one approach to additive fabrication, known as
stereolithography, solid objects are created by successively
forming thin layers of a curable polymer resin, typically first
onto a substrate and then one on top of another. Exposure to
actinic radiation cures a thin layer of liquid resin, which causes
it to harden and adhere to previously cured layers and the bottom
surface of the build platform.
SUMMARY
[0004] Systems and methods for separating a part from a surface
during additive fabrication, are provided.
[0005] Some embodiments include a method of additive fabrication
wherein a plurality of layers of material are formed on a build
platform, comprising forming a layer of material in contact with a
container; and subsequent to the forming of the layer of material,
rotating the container relative to the build platform and moving
the build platform relative to the container, thereby creating an
effective fulcrum about an axis, wherein the rotating of the
container and moving of the build platform causes the layer of
material to separate from the container.
[0006] Some embodiments provide an additive fabrication apparatus
configured to form a plurality of layers of material on a build
platform, comprising a container, the build platform, one or more
actuators, and at least one controller configured to rotate the
container relative to the build platform via at least one of the
one or more actuators, move the build platform relative to the
container via at least one of the one or more actuators, and
subsequent to formation of a layer of material in contact with the
container, rotate the container and move the build platform,
thereby creating an effective fulcrum about an axis, wherein the
rotating of the container and moving of the build platform causes
the layer of material to separate from the container.
[0007] Some embodiments provide at least one computer readable
medium comprising instructions that, when executed, perform a
method of additive fabrication wherein a plurality of layers of
material are formed on a build platform, the method comprising
forming a layer of material in contact with a container, and
subsequent to the forming of the layer of material, rotating the
container relative to the build platform and moving the build
platform relative to the container, thereby creating an effective
fulcrum about an axis, wherein the rotating of the container and
moving of the build platform causes the layer of material to
separate from the container.
[0008] The foregoing summary is provided by way of illustration and
is not intended to be limiting.
BRIEF DESCRIPTION OF DRAWINGS
[0009] The accompanying drawings are not intended to be drawn to
scale. In the drawings, each identical or nearly identical
component that is illustrated in various figures is represented by
a like numeral. For purposes of clarity, not every component may be
labeled in every drawing. In the drawings:
[0010] FIG. 1 provides a schematic view of a stereolithographic
printer, according to some embodiments;
[0011] FIG. 2 provides a schematic view of a stereolithographic
printer having formed a plurality of layer of a part, according to
some embodiments;
[0012] FIG. 3A illustrates a mechanical peel operation of a
stereolithographic printer, according to some embodiments;
[0013] FIG. 3B illustrates formation of an effective fulcrum during
a mechanical peel operation of a stereolithographic printer,
according to some embodiments;
[0014] FIG. 4A illustrates formation of an effective fulcrum by use
of a relocatable axis, according to some embodiments;
[0015] FIG. 4B illustrates formation of an effective fulcrum by a
relocatable axis, according to some embodiments;
[0016] FIG. 5 illustrates formation of an effective fulcrum a
distance from a fixed axis, according to some embodiments;
[0017] FIG. 6 provides a schematic view of dimensions of a
stereolithographic printer, according to some embodiments;
[0018] FIG. 7 illustrates a flow chart of a process suitable for
separating a part from a surface during additive fabrication,
according to some embodiments; and
[0019] FIG. 8 illustrates an example of a computing system
environment on which aspects of the invention may be
implemented.
DETAILED DESCRIPTION
[0020] Systems and methods for separating a part from a surface
during additive fabrication are provided. As discussed above, in
additive fabrication a plurality of layers of material may be
formed on a build platform. In some cases, one or more of the
layers may be formed so as to be in contact with a surface other
than another layer or the build platform. For example,
stereolithographic techniques may form a layer of resin so as to be
in contact with an additional surface, such as a container in which
liquid resin is located.
[0021] To illustrate one exemplary additive fabrication technique
in which a part is formed in contact with a surface other than
another layer or the build platform, an inverse stereolithographic
printer is depicted in FIGS. 1 and 2. Exemplary stereolithographic
printer 100 forms a part in a downward facing direction such that
layers of the part are formed in contact with a surface of a
container into which the liquid resin is held in addition to a
previously cured layer or the build platform. In the example of
FIGS. 1 and 2, stereolithographic printer 100 comprises support
structure 2, build platform 4, container 6, axis 8 and liquid resin
10. In the example of FIGS. 1-2, a downward facing build platform 4
opposes the floor of a container filled with a photopolymer resin
10. FIG. 1 represents a configuration of stereolithographic printer
100 prior to formation of any layers of a part on build platform
4.
[0022] As shown in FIG. 2, a part 12 may be formed layerwise, with
the initial layer attached to the build platform 4. The container's
floor is transparent to actinic radiation, which can then be
targeted at portions of the thin layer of liquid photocurable resin
resting on the floor of the container. Exposure to actinic
radiation cures a thin layer of liquid resin 14, which causes it to
harden. The layer 14 is at least partially in contact with both a
previously formed layer and the surface of the container 6 when it
is formed. The top side of the cured resin layer typically bonds to
either the bottom surface of the build platform 4 or with the
previously cured resin layer in addition to the transparent floor
of the container 14. In order to form additional layers of the part
subsequent to the formation of layer 14, any bonding that occurs
between the transparent floor of the container and the layer must
be broken. For example, one or more portions of the surface (or all
of the surface) of layer 14 may adhere to the container such that
the adhesion must be removed prior to formation of a subsequent
layer.
[0023] Techniques for reducing the strength of this bond may
include inhibiting the curing process or providing a highly smooth
surface on the inside of the container. In many use cases, however,
at least some force must be applied to remove the cured resin layer
from the container floor. For example, a force may be applied by
rotating the container to mechanically separate, or "peel," the
container from the part 12. FIG. 3A depicts an exemplary
stereolithographic printer that separates a part from the container
by pivoting the container 6 about a fixed axis 8 on one side of the
container, thereby displacing an end of the container distal to the
fixed axis a distance 18 (which may be any suitable distance).
Exemplary stereolithographic printer 300 also comprises support
structure 2, build platform 4 and liquid resin 10. This "peeling"
step involves a rotation of the container 6 away from the part 12
to separate layer 16 from the container, which may be followed by a
rotation of the container back towards the part. In addition, the
build platform 4 may move away from the container to create a space
for a new layer of liquid resin to form between the part and the
container. Subsequent to this motion, a new layer of liquid resin
is available for exposure and addition to the part being formed.
Each step of the aforementioned curing and peeling processes may
continue until the part is fully created.
[0024] By progressively separating the part and the container base,
such as in the peeling step described above, the total force
necessary to separate the part and container may be controlled. If
the parts were completely rigid, such a configuration would result
in simultaneous separation across the face of the part, as rotation
of the container about the fixed axis would result in an
instantaneous velocity normal to the face of the part. However, if
the part is at least somewhat elastic (which is typical in
stereolithographic printing, for example), a separation using this
method may not begin until a small deflection of the container has
been performed. This may have an effect that a region of the part
furthest from the fixed axis tends to separate from the container
base prior to the separation of other regions of the part from the
container. As a result, a progression separation may require less
overall force to separate the part from the container compared with
a peel that separates all regions of the part from the container at
the same time. In addition, a progressive separation may mitigate
certain suction forces caused by the void introduced by part
separation by allowing resin, air, or other fluids to flow into the
void.
[0025] The inventors have recognized and appreciated that multiple
problems may arise due to the application of force during the
above-described peeling process. For example, in some use cases a
force may be applied to, and/or through, the part itself. A force
applied to the part may, in some use cases, cause the part to
separate partially or totally from the build platform, rather than
the container, which may disrupt the formation process. In some use
cases, a force applied to the part may cause deformation or
mechanical failure in the part itself.
[0026] The inventors have further recognized and appreciated that
the above-described problems with the peeling process may increase
as a region of a part is located further from the axis of rotation.
For example, increased mechanical forces that result at greater
distances from the axis of rotation may cause a more rapid peel of
the part from a surface, which may more readily cause the
above-described problems. Accordingly, the inventors have
recognized and appreciated that forces applied to a part being
formed may be reduced, thereby reducing disruption to the formation
process, by locating an effective fulcrum adjacent to, or close to,
the part being formed. With such a fulcrum, the part is close to
the axis of rotation, which thereby reduces the forces exerted on
the part during a process of separating the part from a container
compared with an axis located further from the part.
[0027] In some embodiments, an effective fulcrum may be
mechanically formed such that separation of a part from a container
is achieved by moving the container alone. A container mechanically
configured to rotate about any axis along a length of the container
may be able to reduce forces applied to a part during separation by
choosing a suitable axis location, such as a location close to, or
adjacent to, a region of the part. For example, an axis may be
identified as adjacent to an edge of a layer of a part just formed
that is in contact with the container. By rotating the container
about this axis, the just-formed layer may be separated from the
container while reducing forces exerted on the part during
separation.
[0028] In some embodiments, an effective fulcrum may be formed such
that separation of a part from a container is achieved by moving
both the container and build platform. In some use cases, it may be
mechanically difficult and/or expensive to configure the container
to rotate about any chosen axis along its length, and an equivalent
fulcrum may instead be formed by simultaneously moving the
container and build platform such that the net result is the
container rotating relative to the part about the chosen axis.
Since the relative motion of the container and part are equivalent
to the above-discussed case where only the container moves, this
approach of forming an effective fulcrum may similarly reduce
forces exerted on the part during separation. In such an approach,
the container may move about a fixed axis, such as at an end of the
container, and the movement of the build platform may be
coordinated with the rotation of the container about the fixed axis
so as to form the effective fulcrum at a chosen location.
[0029] In embodiments in which the container and the build platform
both move, the container may rotate about the fixed axis in either
direction such that the motion of the build platform is coordinated
to create the effective fulcrum. For example, the container may
rotate in a counterclockwise direction while the build platform
moves away from the container, or the container may rotate in a
clockwise direction while the build platform moves towards the
container. Any of these motions may be performed any number of
times during formation of a single part, as it may be beneficial to
form an effective fulcrum at different locations at different times
during the formation.
[0030] Irrespective of whether the container and/or build platform
move to create the effective fulcrum, the container and/or build
platform may move at any speed and in any direction or directions
such that the effective fulcrum is created. For example, in
embodiments in which the build platform moves, it may move in any
direction including directions towards the container and directions
away from the container (which need not be perpendicular to the
floor of the container. The container and/or build platform may
move at different velocities for various stages of the separation
process. For example, the container may move at a first velocity
during an initial portion of the separation of the part from the
container, and at a second velocity, different from the first
velocity, during a subsequent portion of the separation.
[0031] Subsequent to the part being separated from the container,
the container and/or build platform may move in preparation for a
subsequent layer of the part being formed. This movement may be a
reverse motion of the motion used to separate the part from the
container, though may alternatively be a different motion. In
embodiments in which the container and part both move, any motion
of the container and part subsequent to the separation of the
container and part may, or may not, be coordinated in the manner
described above for creating an effective fulcrum. For example, it
may be beneficial to move the container and/or part to a new
position in preparation for forming a new layer of the part more
rapidly than the motion used to separation the container from the
part, e.g., to reduce the total time needed to form the part.
[0032] In some embodiments, motion of the container and/or the
build platform is controlled by one or more actuators. The one or
more actuators may be controlled by any number of suitable
controllers, including one or more general purpose processors,
Application Specific Integrated Circuits (ASICs),
Field-Programmable Gate Arrays (FPGAs) and/or combinations
thereof.
[0033] In some embodiments, a position of an effective fulcrum may
be determined, at least in part, based on the geometry of a part
being formed. This may include the geometry of the part at a stage
during fabrication (e.g., may include the geometry of the partially
fabricated object) and/or may include a portion of this geometry.
For example, a geometry of the most recently formed layer of the
part may be used, at least in part, to determine a position of an
effective fulcrum to separate the layer from a container. As
another example, the previously formed N (where N>1) layers of
the part may be used, at least in part, to determine a position of
an effective fulcrum to separate the most recently formed layer
from the container.
[0034] Following below are more detailed descriptions of various
concepts related to, and embodiments of, systems and methods for
separating a part from a surface during additive fabrication. It
should be appreciated that various aspects described herein may be
implemented in any of numerous ways. Examples of specific
implementations are provided herein for illustrative purposes only.
In addition, the various aspects described in the embodiments below
may be used alone or in any combination, and are not limited to the
combinations explicitly described herein.
[0035] Although the embodiments herein are primarily disclosed with
respect to the Form 1 3D Printer sold by Formlabs, Inc., the
Assignee of the present application, and with respect to
stereolithography, those having ordinary skill in the art will
appreciate that the invention may be applicable to other systems.
In some embodiments, structures fabricated via one or more additive
fabrication techniques as described herein may be formed from, or
may comprise, a plurality of layers. For example, layer-based
additive fabrication techniques may fabricate an object by formed a
series of layers, which may be detectable through observation of
the object, and such layers may be any size, including any
thickness between 10 microns and 500 microns. In some use cases, a
layer-based additive fabrication technique may fabricate an object
that includes layers of different thickness.
[0036] Although particular systems and methods for separating a
part from a surface during additive fabrication have been described
and shown herein, it is envisioned that the functionality of the
various methods, systems, apparatus, objects, and computer readable
media disclosed herein may be applied to any now known or hereafter
devised additive fabrication technique wherein it is desired to
separate a part from a surface during fabrication.
[0037] As discussed above, the inventors have recognized and
appreciated that multiple problems may arise due to the application
of force during the peeling process described above and depicted in
FIG. 3A. In particular, as shown in FIG. 3B, the illustrative
example provided in FIG. 3A typically forms a Class 2 lever,
wherein an effective fulcrum 44 is located at the fixed axis 8.
Because of this configuration, the mechanical advantage of the
lever tends to increase the magnitude of the peel forces applied to
areas of the part 12 further away from the fixed axis 8. This
increase in the applied force may be undesirable, as it may lead to
increased part 12 distortion and failure.
[0038] FIG. 4A depicts an inverse stereolithographic process that
forms an effective fulcrum a distance from an end of a container,
according to some embodiments. In the example of FIG. 4A, an axis 8
can be mechanically relocated along the based of container 6.
Exemplary inverse stereolithographic printer 400 comprises support
structure 2, build platform 4 and liquid resin 10. The container 6
may be rotated about axis 8 by any suitable amount thereby
displacing an end of the container a distance 18 (which may be any
suitable distance) and separating a layer 16 of part 12 from the
container. For example, the axis may be relocated based on the
location of the part 12 on build platform 4. As discussed above,
selecting an effective fulcrum to be closer to a part being formed
by moving the axis of rotation, as depicted in FIG. 4B, may improve
part quality and device performance.
[0039] According to some embodiments, the fixed axis 8 is not
movable, which may for example avoid additional complexity and cost
of such a movable feature. Instead, as depicted in exemplary FIG.
5, one embodiment of the present invention creates an effective
fulcrum 44 at a different location to the fixed axis 8 by
simultaneously moving the build platform a distance 42.
[0040] As illustrated by the example of FIG. 5, an effective
fulcrum 44 may be created in the reference frame of the part being
formed by a coordinated movement depicted by displacement 42 of the
build platform 4 while the container 6 is pivoted down thereby
displacing the container a distance 18 (which may be any suitable
distance) about the fixed axis 8. Exemplary stereolithographic
printer 500 shown in FIG. 5 comprises support structure 2, build
platform 4 and liquid resin 10. While the actual fulcrum of the
motion remains at the fixed axis 8, the coordinated downwards
motion depicted by displacement 42 of the build platform 4 results
in a force profile that approximates a fulcrum 44 located further
in from the fixed axis 8.
[0041] In some embodiments, coordinated motion of the build
platform and container may be achieved via software controlling the
motions of the build platform 4 and container 6 to locate the
effective fulcrum 44 at a range of locations (e.g., via one or more
actuators coupled to the build platform and container). For
example, such motion may be orchestrated with a number of physical
systems, including by use of open-loop systems such as stepper
motors or closed-loop systems such as servomotors.
[0042] According to some embodiments, motion of a container and/or
a build platform may be based, at least in part, on one or more
dimensions of the system. FIG. 6 provides an illustrative example
of a system, depicting several such dimensions, any number of which
may be used to determine a motion (e.g., velocity, acceleration,
timing of motion, etc.) of a container and/or build platform.
[0043] In the example of FIG. 6, the distance between a fixed axis
8 and the closer edge of the build platform 4 is represented as
d.sub.H, the width of the build platform 4 in a direction
perpendicular to the fixed axis 8 and parallel to the plane of the
build platform is represented as d.sub.BP, and the distance between
the edge of the build platform opposite the fixed axis 8 and the
point at which downwards force is applied to the lever is
represented as d.sub.M.
[0044] It will be appreciated that, while some dimensions such as
those discussed above may be substantially constant for a given
system, other relevant dimensions may depend on the geometry of the
desired part 12, and accordingly may, in some use cases, vary layer
by layer during the operation of the machine. For example, the
distance between the fixed axis 8 and the effective fulcrum 44
(whose position may be chosen based at least in part on one or more
of the dimensions shown in FIG. 6, for example) represented by
d.sub.x may be adjusted during the operation of the print process
(e.g., based on the geometry of the part
[0045] In the example of FIG. 6, a distance the container 6 is
moved down represented as d.sub.p, and the velocity at which the
container 6 is moved down, represented by v.sub.p, may also change
during the operation of the printing process. For example, during a
first peel operation the container may move a first distance down
at a first velocity, and during a second peel operation, the
container may move a second distance, different from the first
distance, down at a second velocity, different from the first
velocity.
[0046] As discussed above, a location of an effective fulcrum may
be chosen to reduce forces applied to a part 12 during separation
of the part from container 6. In the example of FIG. 6, the
location of the effective fulcrum 44 is characterized by a distance
d.sub.x from a fixed axis 8. In some embodiments, d.sub.x may be
set to be d.sub.H, thus moving the effective fulcrum 44 to the edge
of the build platform.
[0047] In some embodiments, d.sub.x may be calculated based on the
geometry of one or more layers of part 12. For example, d.sub.x may
be calculated based on the minimum, maximum, or average of d.sub.x
that was used for one or more of the previously-formed layers. As
one non-limiting example, d.sub.x may be calculated based on a
distance from the fixed axis 8 and the edge of the most recently
formed layer closest to the fixed axis along a line perpendicular
to the fixed axis 8 and parallel to the plane of the build
platform.
[0048] In some embodiments, d.sub.x is set to be close to, but not
adjacent to, a part being formed. This may, for example, avoid
damage to the part due to excess compression during the peel
operation caused by the container pushing against and/or pulling at
the part. As a non-limiting example, d.sub.x may be calculated
based on a distance from the fixed axis 8 and the closest edge of
the layer to the fixed axis to be formed N layers after the current
layer L so as to avoid damage to the part due to excess compression
during the peel operation. A sufficient value of N can be
calculated using the following equation, where d.sub.part
represents the greatest width of the part formed so far across the
build platform, normal to the fixed axis 8, and t.sub.layer
represents the layer height used in the formation process:
N = d rel t layer ##EQU00001## where ##EQU00001.2## d rel = tan (
.theta. max ) d part ##EQU00001.3## .theta. max = atan ( d P d H +
d BP + d M ) ##EQU00001.4##
[0049] In some embodiments, a value of d.sub.x may be determined by
calculating the convex hull of the union of the portion of the part
12 already formed and the build platform 4 in the plane normal to
the fixed axis 8. Using said convex hull, d.sub.x is set such that
d.sub.x is a given offset distance closer to the fixed axis 8 than
the closest vertex of said convex hull. This may, for example,
provide an effective fulcrum that is close, but not adjacent to, to
the part being formed while ensuring it is in a location in which
an effective fulcrum can be created by motion of the build platform
and container.
[0050] The effective fulcrum 44 may be created at a distance
d.sub.x from the fixed axis by lowering the build platform 4
towards the container 6 at any suitable speed or speeds and over
any suitable distance. In some embodiments, the movement of the
build platform 4 and container 6 may be physically or logically
coupled to provide a synchronized motion of the build platform and
container. For example, each may be controlled by one or more
open-loop stepper motor systems configured to move such that the
resulting combined motion of the container and build platform
combined approximates the motion of a true fixed axis 8 located at
the effective fulcrum 44 point. In the example of FIG. 6, the
effective fulcrum 44 may be located at d.sub.x by pivoting the
container 6 down a distance of d.sub.p at a velocity of v.sub.p
while simultaneously moving the build platform 4 down a distance of
distance of d.sub.px at a velocity of v.sub.px wherein d.sub.px and
v.sub.px are governed by the following equations:
h = d x d H + d BP + d M ##EQU00002## d px = d p h ##EQU00002.2## v
px = v p h ##EQU00002.3##
[0051] In some embodiments, the movement of the build platform 4
may be expressed in terms of a ratio between the motion of the
container 6 and the build platform 4. For example, in an open-loop
stepper motor configuration, the build platform 4 may be lowered by
individual steps for every K steps that the container is rotated.
In some use cases, K may be chosen based on the parameters of the
step motors and geometry of the machine such that it closely
approximates h, as calculated above.
[0052] In some embodiments, upon the completion of the peeling
process described above, the build platform 4 and part 12 may
extend below the position of the container 6 when horizontal. The
build platform 4 may then be raised to prepare for forming a
subsequent layer. For example, the build platform may be raised at
least a distance d.sub.px in a vertical direction in order to
return the build platform 4 to the location it would otherwise have
but for the movements performed during the peel operation.
Following such a return move, the container 6 may, additionally or
alternatively, be returned to a horizontal orientation. In some
embodiments, the return motions of the build platform 4 and
container 6 may be coordinated such that both move at a reciprocal
direction and speed from the motions described above during the
peel process. In such cases, however, it may be beneficial for the
build platform to be further raised a preset distance to avoid
reattaching the most recently formed layer of the part 12 to the
bottom of the container 6.
[0053] Although aspects of the present invention described herein
may describe an effective fulcrum being formed between the fixed
axis 8 and part 12 such that the container rotates in a downward
direction (e.g., clockwise in the example of FIG. 6), other
embodiments of the same invention may form the effective fulcrum 44
such that the direction of the peeling operation is reversed. For
example, d.sub.p may be negative, representing a tilt of the
container 6 up, rather than down, above a horizontal starting
plane. If d.sub.x is then set so as to be closer to the edge of the
container 6 furthest from the fixed axis 8, the peeling separation
of the part 12 from the container 6 may begin along the edge of the
part 12 closest to the fixed axis 8, rather than furthest from it
as is the case in certain examples described above. Thus the
effective fulcrum 44 may be moved such that the container appears
to pivot from the side opposite from the fixed axis 8 without
requiring mechanical changes or duplication of the fixed axis 8.
Such a configuration may advantageously allow for additional
options for part removal and the distribution of wear on the
container 6 lower surface.
[0054] FIG. 7 illustrates a flow chart of a process suitable for
separating a part from a surface during additive fabrication,
according to some embodiments. Method 700 may be performed by any
suitable additive fabrication apparatus, including but not limited
to a stereolithographic printer as described above, for example in
the exemplary embodiment shown in FIG. 5.
[0055] In act 701, a first layer of material is formed via additive
fabrication. The first layer of material may be formed at any time
during additive fabrication of a part. For example, the first layer
may be the sole layer formed (e.g., on a build platform), or may be
the most recently formed layer and may be in contact with one or
more previously formed layers.
[0056] In act 702, an effective fulcrum is created by moving the
container and the build platform. As discussed above in relation to
FIG. 5, by coordinating the movement of the container about a fixed
axis with movement of the build platform, an effective fulcrum may
be created a distance from the fixed axis. In act 702, an effective
fulcrum may be formed in this manner, which causes at least the
first layer of material to separate from the contained via the peel
operation described above in act 703.
[0057] FIG. 8 illustrates an example of a suitable computing system
environment 800 on which aspects of the invention may be
implemented. For example, the computing system environment 800 may
be used to determine the supportedness of one or more regions of an
object, to generate a support structure for an object, to generate
support tips for a support structure, to indicate the supportedness
of one or more regions of an object via a graphical user interface,
to interface with one or more devices to effect additive
fabrication of an object and/or a support structure, or any
combinations thereof. Such a computing environment may represent a
home computer, a tablet, a mobile device, a server and/or any
another computing device.
[0058] The computing system environment 800 is only one example of
a suitable computing environment and is not intended to suggest any
limitation as to the scope of use or functionality of the
invention. Neither should the computing environment 800 be
interpreted as having any dependency or requirement relating to any
one or combination of components illustrated in the exemplary
operating environment 800.
[0059] Aspects of the invention are operational with numerous other
general purpose or special purpose computing system environments or
configurations. Examples of well-known computing systems,
environments, and/or configurations that may be suitable for use
with the invention include, but are not limited to, personal
computers, server computers, hand-held or laptop devices,
multiprocessor systems, microprocessor-based systems, set top
boxes, programmable consumer electronics, network PCs,
minicomputers, mainframe computers, distributed computing
environments that include any of the above systems or devices, and
the like.
[0060] The computing environment may execute computer-executable
instructions, such as program modules. Generally, program modules
include routines, programs, objects, components, data structures,
etc. that perform particular tasks or implement particular abstract
data types. The invention may also be practiced in distributed
computing environments where tasks are performed by remote
processing devices that are linked through a communications
network. In a distributed computing environment, program modules
may be located in both local and remote computer storage media
including memory storage devices.
[0061] With reference to FIG. 8, an exemplary system for
implementing aspects of the invention includes a general purpose
computing device in the form of a computer 810. Components of
computer 810 may include, but are not limited to, a processing unit
820, a system memory 830, and a system bus 821 that couples various
system components including the system memory to the processing
unit 820. The system bus 821 may be any of several types of bus
structures including a memory bus or memory controller, a
peripheral bus, and a local bus using any of a variety of bus
architectures. By way of example, and not limitation, such
architectures include Industry Standard Architecture (ISA) bus,
Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus,
Video Electronics Standards Association (VESA) local bus, and
Peripheral Component Interconnect (PCI) bus also known as Mezzanine
bus.
[0062] Computer 810 typically includes a variety of computer
readable media. Computer readable media can be any available media
that can be accessed by computer 810 and includes both volatile and
nonvolatile media, removable and non-removable media. By way of
example, and not limitation, computer readable media may comprise
computer storage media and communication media. Computer storage
media includes both volatile and nonvolatile, removable and
non-removable media implemented in any method or technology for
storage of information such as computer readable instructions, data
structures, program modules or other data. Computer storage media
includes, but is not limited to, RAM, ROM, EEPROM, flash memory or
other memory technology, CD-ROM, digital versatile disks (DVD) or
other optical disk storage, magnetic cassettes, magnetic tape,
magnetic disk storage or other magnetic storage devices, or any
other medium which can be used to store the desired information and
which can accessed by computer 810. Communication media typically
embodies computer readable instructions, data structures, program
modules or other data in a modulated data signal such as a carrier
wave or other transport mechanism and includes any information
delivery media. The term "modulated data signal" means a signal
that has one or more of its characteristics set or changed in such
a manner as to encode information in the signal. By way of example,
and not limitation, communication media includes wired media such
as a wired network or direct-wired connection, and wireless media
such as acoustic, RF, infrared and other wireless media.
Combinations of the any of the above should also be included within
the scope of computer readable media.
[0063] The system memory 830 includes computer storage media in the
form of volatile and/or nonvolatile memory such as read only memory
(ROM) 831 and random access memory (RAM) 832. A basic input/output
system 833 (BIOS), containing the basic routines that help to
transfer information between elements within computer 810, such as
during start-up, is typically stored in ROM 831. RAM 832 typically
contains data and/or program modules that are immediately
accessible to and/or presently being operated on by processing unit
820. By way of example, and not limitation, FIG. 8 illustrates
operating system 834, application programs 835, other program
modules 836, and program data 837.
[0064] The computer 810 may also include other
removable/non-removable, volatile/nonvolatile computer storage
media. By way of example only, FIG. 8 illustrates a hard disk drive
841 that reads from or writes to non-removable, nonvolatile
magnetic media, a magnetic disk drive 851 that reads from or writes
to a removable, nonvolatile magnetic disk 852, and an optical disk
drive 855 that reads from or writes to a removable, nonvolatile
optical disk 856 such as a CD ROM or other optical media. Other
removable/non-removable, volatile/nonvolatile computer storage
media that can be used in the exemplary operating environment
include, but are not limited to, magnetic tape cassettes, flash
memory cards, digital versatile disks, digital video tape, solid
state RAM, solid state ROM, and the like. The hard disk drive 841
is typically connected to the system bus 821 through an
non-removable memory interface such as interface 840, and magnetic
disk drive 851 and optical disk drive 855 are typically connected
to the system bus 821 by a removable memory interface, such as
interface 850.
[0065] The drives and their associated computer storage media
discussed above and illustrated in FIG. 8, provide storage of
computer readable instructions, data structures, program modules
and other data for the computer 810. In FIG. 8, for example, hard
disk drive 841 is illustrated as storing operating system 844,
application programs 845, other program modules 846, and program
data 847. Note that these components can either be the same as or
different from operating system 834, application programs 835,
other program modules 836, and program data 837. Operating system
844, application programs 845, other program modules 846, and
program data 847 are given different numbers here to illustrate
that, at a minimum, they are different copies. A user may enter
commands and information into the computer 810 through input
devices such as a keyboard 862 and pointing device 861, commonly
referred to as a mouse, trackball or touch pad. Other input devices
(not shown) may include a microphone, joystick, game pad, satellite
dish, scanner, or the like. These and other input devices are often
connected to the processing unit 820 through a user input interface
860 that is coupled to the system bus, but may be connected by
other interface and bus structures, such as a parallel port, game
port or a universal serial bus (USB). A monitor 891 or other type
of display device is also connected to the system bus 821 via an
interface, such as a video interface 890. In addition to the
monitor, computers may also include other peripheral output devices
such as speakers 897 and printer 896, which may be connected
through a output peripheral interface 895.
[0066] The computer 810 may operate in a networked environment
using logical connections to one or more remote computers, such as
a remote computer 880. The remote computer 880 may be a personal
computer, a server, a router, a network PC, a peer device or other
common network node, and typically includes many or all of the
elements described above relative to the computer 810, although
only a memory storage device 881 has been illustrated in FIG. 8.
The logical connections depicted in FIG. 8 include a local area
network (LAN) 871 and a wide area network (WAN) 873, but may also
include other networks. Such networking environments are
commonplace in offices, enterprise-wide computer networks,
intranets and the Internet.
[0067] When used in a LAN networking environment, the computer 810
is connected to the LAN 871 through a network interface or adapter
870. When used in a WAN networking environment, the computer 810
typically includes a modem 872 or other means for establishing
communications over the WAN 873, such as the Internet. The modem
872, which may be internal or external, may be connected to the
system bus 821 via the user input interface 860, or other
appropriate mechanism. In a networked environment, program modules
depicted relative to the computer 810, or portions thereof, may be
stored in the remote memory storage device. By way of example, and
not limitation, FIG. 8 illustrates remote application programs 885
as residing on memory device 881. It will be appreciated that the
network connections shown are exemplary and other means of
establishing a communications link between the computers may be
used.
[0068] The various methods or processes outlined herein may be
implemented in any suitable hardware. Additionally, the various
methods or processes outlined herein may be implemented in a
combination of hardware and of software executable on one or more
processors that employ any one of a variety of operating systems or
platforms. For example, the various methods or processes may
utilize software to instruct a processor to determine the
supportedness of one or more regions of an object to be fabricated
via one or more additive fabrication techniques; and/or to generate
a support structure, with or without support tips, for an object to
be fabricated via one or more additive fabrication techniques.
Example of such approaches are described above. However, any
suitable combination of hardware and software may be employed to
realize any of the embodiments discussed herein.
[0069] In this respect, various inventive concepts may be embodied
as at least one non-transitory computer readable storage medium
(e.g., a computer memory, one or more floppy discs, compact discs,
optical discs, magnetic tapes, flash memories, circuit
configurations in Field Programmable Gate Arrays or other
semiconductor devices, etc.) encoded with one or more programs
that, when executed on one or more computers or other processors,
implement the various embodiments of the present invention. The
non-transitory computer-readable medium or media may be
transportable, such that the program or programs stored thereon may
be loaded onto any computer resource to implement various aspects
of the present invention as discussed above.
[0070] The terms "program" or "software" are used herein in a
generic sense to refer to any type of computer code or set of
computer-executable instructions that can be employed to program a
computer or other processor to implement various aspects of
embodiments as discussed above. Additionally, it should be
appreciated that according to one aspect, one or more computer
programs that when executed perform methods of the present
invention need not reside on a single computer or processor, but
may be distributed in a modular fashion among different computers
or processors to implement various aspects of the present
invention.
[0071] Computer-executable instructions may be in many forms, such
as program modules, executed by one or more computers or other
devices. Generally, program modules include routines, programs,
objects, components, data structures, etc. that perform particular
tasks or implement particular abstract data types. Typically, the
functionality of the program modules may be combined or distributed
as desired in various embodiments.
[0072] Various inventive concepts may be embodied as one or more
methods, of which examples have been provided. For example, methods
of separating a part from a surface during additive fabrication
have been provided herein. The acts performed as part of any method
described herein may be ordered in any suitable way. Accordingly,
embodiments may be constructed in which acts are performed in an
order different than illustrated, which may include performing some
acts simultaneously, even though these acts may have been shown as
sequential acts in illustrative embodiments.
[0073] All definitions, as defined and used herein, should be
understood to control over dictionary definitions, definitions in
documents incorporated by reference, and/or ordinary meanings of
the defined terms.
[0074] The indefinite articles "a" and "an," as used herein, unless
clearly indicated to the contrary, should be understood to mean "at
least one."
[0075] As used herein, the phrase "at least one," in reference to a
list of one or more elements, should be understood to mean at least
one element selected from any one or more of the elements in the
list of elements, but not necessarily including at least one of
each and every element specifically listed within the list of
elements and not excluding any combinations of elements in the list
of elements. This definition also allows that elements may
optionally be present other than the elements specifically
identified within the list of elements to which the phrase "at
least one" refers, whether related or unrelated to those elements
specifically identified.
[0076] The phrase "and/or," as used herein, should be understood to
mean "either or both" of the elements so conjoined, i.e., elements
that are conjunctively present in some cases and disjunctively
present in other cases. Multiple elements listed with "and/or"
should be construed in the same fashion, i.e., "one or more" of the
elements so conjoined. Other elements may optionally be present
other than the elements specifically identified by the "and/or"
clause, whether related or unrelated to those elements specifically
identified. Thus, as a non-limiting example, a reference to "A
and/or B", when used in conjunction with open-ended language such
as "comprising" can refer, in one embodiment, to A only (optionally
including elements other than B); in another embodiment, to B only
(optionally including elements other than A); in yet another
embodiment, to both A and B (optionally including other elements);
etc.
[0077] As used herein, "or" should be understood to have the same
meaning as "and/or" as defined above. For example, when separating
items in a list, "or" or "and/or" shall be interpreted as being
inclusive, i.e., the inclusion of at least one, but also including
more than one, of a number or list of elements, and, optionally,
additional unlisted items. Only terms clearly indicated to the
contrary, such as "only one of" or "exactly one of," will refer to
the inclusion of exactly one element of a number or list of
elements. In general, the term "or" as used herein shall only be
interpreted as indicating exclusive alternatives (i.e. "one or the
other but not both") when preceded by terms of exclusivity, such as
"either," "one of," "only one of," or "exactly one of."
[0078] The phraseology and terminology used herein is for the
purpose of description and should not be regarded as limiting. The
use of "including," "comprising," "having," "containing",
"involving", and variations thereof, is meant to encompass the
items listed thereafter and additional items.
[0079] Having described several embodiments of the invention in
detail, various modifications and improvements will readily occur
to those skilled in the art.
[0080] For example, techniques of separating a portion of a part
formed through additive fabrication from a surface were described.
These techniques may be applied in other contexts. For example, any
additive fabrication process in which a portion of a part being
formed becomes in any way attached to a surface other than another
portion of the part or a build platform may utilize techniques as
described herein. Such modifications and improvements are intended
to be within the spirit and scope of the invention. Accordingly,
the foregoing description is by way of example only, and is not
intended as limiting.
* * * * *